RVHS 2023 JC2 H2 Prelim P3 A

RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CENTRE NUMBER S CLASS 22J INDEX NUMBER BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 15 September 2023 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE ON ANY BARCODES. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 2 3 Section B Total This document consists of 23 printed pages and 1 blank page.

2 River Valley High School H2 Biology 9744/03 2023 JC2 Preliminary Examination Section A Answer all the questions in this section. 1 The gut microbiota is the community of all micro-organisms (bacteria, archaea, protozoa, fungi, and viruses) present in the digestive tract. Bacteria are the largest component of the microbiota. (a) Describe the structure of bacterial genome. [3] 1. Haploid; 2. Double-stranded; 3. Circular DNA; 4. Associated with basic proteins; 5. Presence of plasmid(s); 6. Few million nucleotides in length; [R: introns] Gut bacteria are present in a range of species in Kingdom Animalia including insects, fish, and apes. Gut bacteria are passed vertically from mother to offspring. Its composition and abundance have changed in the generations with evolutionary time. Fig. 1.1 shows the relative change in abundance of selected bacterial taxa in the evolution of humans ( Homo sapiens ). Relative change is shown by the “_x” in the box beside the descendant species, for example “5x” refers to a five times increase in abundance from the ancestor. 19 MYA 7 MYA 2. 6 MYA Gorilla gorilla Pan paniscus Pan trogolodytes Homo sapiens 5x 2x 0.5x 0.2x 0.2x 0.2x 0.5x 0.5x 5x 5x 2x 2x Bacterial genera present in ancestor Bacteroides Lactobacillus Clostridium Fibrobacter Lactobacillus Lactobacillus Fibrobacter Fibrobacter Bacteroides Clostridium Clostridium Bacteroides Clostridium key MYA: Million years ago

3 River Valley High School H2 Biology 9744/03 2023 JC2 Preliminary Examination Adapted from Moeller et al, PNAS, 111(46), 2014 Fig. 1.1 (b) With reference to the animals in Fig. 1.1, explain how phylogeny is related to classificat